1993 GMC Sierra drive shaft

Sometimes that is specified by the manufacturer to solve an illusive drive line vibration. Sometimes they tell you to switch to a two-piece with a center carrier bearing to do the same thing. First you have to be sure there is proper clearance throughout the range the ride height can travel through. Next, you have to consider that a specific drive line angle is necessary to prevent wear in the u-joint bearing cups, and to prevent setting up a droning-type of vibration of which GM truck owners are all very familiar with. Then you have to find a drive shaft of the correct length or have one custom-made. Very often the right drive shaft isn't even available through the dealer.

You also have to look at the ride height to see if the springs are sagged from age. That changes drive line angle which can be responsible for a vibration that can be real hard to pinpoint.